Hey, I cannot find no one who'll tell me if my team's good so I'll ask here. I will list every Pokémon I have with their movesets. If you find something I can improve on, please tell me (even if my team completly sucks)
Rayquaza: Aerial Ace, Dragon Dance, Earthquake, Dragon Claw
Metagross: Earthquake, Meteor Mash, Aerial Ace, Explosion
Swampert: Earthquake, Surf, Ice Beam, Superpower
Tyranitar: Secret Power, Brick Break, Earthquake, Rock Slide
Salamance: Outrage, Earthquake, Return, Flamethrower
Charizard: Slash, Flamethrower, Earthquake, Fly

Thanks ^-^

Is this team for a regular playthrough or for something else?

Well, you have one major legend, three pseudos, and Swampert being the most OP starter back when Hidden Abilities and Megas didn't exist, so your Pokémon definitely don't lack in stats or individual strength at all... quite the opposite, for ingame purposes they should be enough to destroy everything.

If you want to look at it as a team, however, it looks rather unbalanced to me, with some Pokémon seemingly trying to fulfill a role that another member has already covered. I mean:

Yeah, Earthquake is a great move, but teaching it to an entire party is probably a bit too much.

None of your Pokémon knows anything super effective against Psychic and Ghost, which is strange considering that Tyranitar is Dark type and gets Crunch. Granted Tyranitar's special attack isn't that great, but it's still higher than Swampert's, or than Charizard's physical attack, which do have mixed attacker movesets. Even Metagross could get Shadow Ball, which was physical, replacing Aerial Ace, since you already have other three Pokémon that can make much better use of Flying moves.

You don't have anything super effective against Hoenn's favorite type, Water, either. Could teach Rayquaza Thunderbolt or something.

Rayquaza and Salamence are kind of redundant (Salamence is basically Rayquaza+Charizard). They're both Dragon/Flying (plus a third Flying type with Charizard), both have a 4x weakness to Ice (which none in your team resists except Metagross), and they even have similar movesets.

Normally, I would say that this team isn't good, but I'm not sure what it is meant for. If you're using it for a normal playthrough, it should be great. These Pokémon are all very powerful. The structure of the team can use some improvement though. While I'm not really too familiar with the physical/special mechanics before Generation IV, I can still see that you have way too many physical attackers on your team, and half your team is weak to Rock-type moves because you have three Flying types. Also note that Charizard has a double weakness to Rock-type attacks. I'm assuming that every Pokémon in your party knows Earthquake not just because it is a great easy-to-teach powerful coverage move, but also to address this problem. Yet, understand that Rock-type moves are often used as common coverage, much like Earthquake is. If I was facing you in battle, I could literally beat your team with a good physical defender and literally just Toxic stall you, which was very easy to do back then. If you're just using this team for an in-game playthrough, you're good. Lol I don't think any NPC is beating this team. However, if you're trying to do something like the Battle Tower, it is possible that an NPC might exploit your team's weaknesses, but I wouldn't worry too much about it. If you're trying to battle competitively however, then I would recommend a more balanced team of physical and special attackers.

I'd +1 what Corveone said, but also, what game are you playing where you can get both Swampert and Charizard before the "post game" (basically the areas that are only accessible after the Elite Four)?